Novel Sulfonamides

ABSTRACT

The present invention provides  
                 
     wherein R 1  is selected from the group consisting of C 1 -C 10  alkoxy, OH and NR 4 R 5 ;    R 2  is selected from the group consisting of C 1 -C 10  alkyl and (CH 2 ) n OH;    R 3  is selected from the group consisting of C 1 -C 10  alkyl, heteroaryl, e.g. thienyl, furanyl and pyridyl, phenyl, mono, -di-, tri-substituted phenyl and heteroaryl;    R 4  and R 5  are independently selected from the group consisting of H, C 1 -C 10  alkyl, C 1 -C 10  alkyl hydroxyl; m is 0 or an integer from 1 to 3 and n is an integer of from 1 to 4. These compounds are useful in lowering intraocular pressure and/or treating glaucoma or providing neuroprotection to the eye of a human patient.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on, and claims the benefit of, U.S. Provisional Application No. 60/710,719, filed Aug. 22, 2005, and which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to novel sulfonamide compounds which are useful in lowering intraocular pressure and/or treating glaucoma or may be used in providing neuroprotection to the eye of a human.

2. Description of the Related Art

Ocular hypotensive agents are useful in the treatment of a number of various ocular hypertensive conditions, such as post-surgical and post-laser trabeculectomy ocular hypertensive episodes, glaucoma, and as presurgical adjuncts.

Glaucoma is a disease of the eye characterized by increased intraocular pressure. On the basis of its etiology, glaucoma has been classified as primary or secondary. For example, primary glaucoma in adults (congenital glaucoma) may be either open-angle or acute or chronic angle-closure. Secondary glaucoma results from pre-existing ocular diseases such as uveitis, intraocular tumor or an enlarged cataract.

The underlying causes of primary glaucoma are not yet known. The increased intraocular tension is due to the obstruction of aqueous humor outflow. In chronic open-angle glaucoma, the anterior chamber and its anatomic structures appear normal, but drainage of the aqueous humor is impeded. In acute or chronic angle-closure glaucoma, the anterior chamber is shallow, the filtration angle is narrowed, and the iris may obstruct the trabecular meshwork at the entrance of the canal of Schlemm. Dilation of the pupil may push the root of the iris forward against the angle, and may produce pupillary block and thus precipitate an acute attack. Eyes with narrow anterior chamber angles are predisposed to acute angle-closure glaucoma attacks of various degrees of severity.

Secondary glaucoma is caused by any interference with the flow of aqueous humor from the posterior chamber into the anterior chamber and subsequently, into the canal of Schlemm. Inflammatory disease of the anterior segment may prevent aqueous escape by causing complete posterior synechia in iris bombe and may plug the drainage channel with exudates. Other common causes are intraocular tumors, enlarged cataracts, central retinal vein occlusion, trauma to the eye, operative procedures and intraocular hemorrhage.

Considering all types together, glaucoma occurs in about 2% of all persons over the age of 40 and may be asymptotic for years before progressing to rapid loss of vision. In cases where surgery is not indicated, topical α-adrenoreceptor antagonists have traditionally been the drugs of choice for treating glaucoma.

It has long been know that one of the sequelae of glaucoma is damage to the optic nerve head. This damage, referred to as “cupping”, results in depressions in areas of the nerve fiber of the optic disk. Loss of sight from this cupping is progressive and can lead to blindness if the condition is not treated effectively.

Unfortunately lowering intraocular pressure by administration of drugs or by surgery to facilitate outflow of the aqueous humor is not always effective in obviating damage to the nerves in glaucomatous conditions. This apparent contradiction is addressed by Cioffi and Van Buskirk [Surv. of Ophthalmol., 38, Suppl. p. S107-16, discussion S116-17, May 1994] in the article, “Microvasculature of the Anterior Optic Nerve”. The abstract states:

-   -   The traditional definition of glaucoma as a disorder of         increased intraocular pressure (IOP) oversimplifies the clinical         situation. Some glaucoma patients never have higher than normal         IOP and others continue to develop optic nerve damage despite         maximal lowering of IOP. Another possible factor in the etiology         of glaucoma may be regulation of the regional microvasculature         of the anterior optic nerve. One reason to believe that         microvascular factors are important is that many microvascular         diseases are associated with glaucomatous optic neuropathy.

Subsequent to Cioffi, et al., Matusi published a paper on the “Ophthalmologic aspects of Systemic Vasculitis” [Nippon Rinsho, 52 (8), p. 2158-63, August 1994] and added further support to the assertion that many microvascular diseases are associated with glaucomatous optic neuropathy. The summary states:

-   -   Ocular findings of systemic vasculitis, such as polyarteritis         nodosa, giant cell angitis and aortitis syndrome were reviewed.         Systemic lupus erythematosus is not categorized as systemic         vasculitis, however its ocular findings are microangiopathic.         Therefore, review of its ocular findings was included in this         paper. The most common fundus finding in these diseases is         ischemic optic neuropathy or retinal vascular occlusions.         Therefore several points in diagnosis or pathogenesis of optic         neuropathy and retinal and choroidal vaso-occlusion were         discussed. Choroidal ischemia has come to be able to be         diagnosed clinically, since fluorescein angiography was applied         in these lesions. When choroidal arteries are occluded,         overlying retinal pigment epithelium is damaged. This causes         disruption of barrier function of the epithelium and allows         fluid from choroidal vasculatures to pass into subsensory         retinal spaces. This is a pathogenesis of serous detachment of         the retina. The retinal arterial occlusion formed non-perfused         retina. Such hypoxic retina released angiogenesis factors which         stimulate retinal and iris neovascularizations and iris         neovascularizations may cause neovascular glaucoma.

B. Schwartz, in “Circulatory Defects of the Optic Disk and Retina in Ocular Hypertension and High Pressure Open-Angle Glaucoma” [Surv. Ophthalmol., 38, Suppl. pp. S23-24, May 1994] discusses the measurement of progressive defects in the optic nerve and retina associated with the progression of glaucoma. He states:

-   -   Fluorescein defects are significantly correlated with visual         field loss and retinal nerve fiber layer loss. The second         circulatory defect is a decrease of flow of fluorescein in the         retinal vessels, especially the retinal veins, so that the         greater the age, diastolic blood pressure, ocular pressure and         visual field loss, the less the flow. Both the optic disk and         retinal circulation defects occur in untreated ocular         hypertensive eyes. These observations indicate that circulatory         defects in the optic disk and retina occur in ocular         hypertension and open-angle glaucoma and increase with the         progression of the disease.

Thus, it is evident that there is an unmet need for agents that have neuroprotective effects in the eye that can stop or retard the progressive damage that occurs to the nerves as a result of glaucoma or other ocular afflictions.

Prostaglandins were earlier regarded as potent ocular hypertensives; however, evidence accumulated in the last two decades shows that some prostaglandins are highly effective ocular hypotensive agents and are ideally suited for the long-term medical management of glaucoma. (See, for example, Starr, M. S. Exp. Eye Res. 1971, 11, pp. 170-177; Bito, L. Z. Biological Protection with Prostaglandins Cohen, M. M., ed., Boca Raton, Fla., CRC Press Inc., 1985, pp. 231-252; and Bito, L. Z., Applied Pharmacology in the Medical Treatment of Glaucomas Drance, S. M. and Neufeld, A. H. eds., New York, Grune & Stratton, 1984, pp. 477-505). Such prostaglandins include PGF_(2α), PGF_(1α), PGE₂, and certain lipid-soluble esters, such as C₁ to C₅ alkyl esters, e.g. 1-isopropyl ester, of such compounds.

BRIEF SUMMARY OF THE INVENTION

The present invention provides compounds represented by the formula:

-   wherein R¹ is selected from the group consisting of C₁-C₁₀ alkoxy,     OH and NR⁴R⁵; -   R² is selected from the group consisting of C₁-C₁₀ alkyl and     (CH₂)_(n)OH; -   R³ is selected from the group consisting of C₁-C₁₀ alkyl,     heteroaryl, e.g. thienyl, furanyl and pyridyl, phenyl, mono, -di-,     tri-substituted phenyl and heteroaryl; -   R⁴ and R⁵ are independently selected from the group consisting of H,     C₁-C₁₀ alkyl, C₁-C₁₀ alkyl hydroxyl; -   m is 0 or an integer from 1 to 3 and -   n is an integer of from 1 to 4.     These compounds may be used in lowering intraocular pressure and/or     treating glaucoma or may be used in providing neuroprotection to the     eye of a human.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 describes a general synthetic scheme for the preparation of certain intermediates useful in the preparation of the compounds of the invention.

FIG. 2 describes a general synthetic scheme for the preparation of certain of the compounds of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The novel compounds of the present invention have the general formula

-   wherein R¹ is selected from the group consisting of C₁-C₁₀ alkoxy,     OH and NR⁴R⁵; -   R² is selected from the group consisting of C₁-C₁₀ alkyl and     (CH₂)_(n)OH; -   R³ is selected from the group consisting of C₁-C₁₀ alkyl,     heteroaryl, e.g. thienyl, furanyl and pyridyl, phenyl, mono, -di-,     tri-substituted phenyl and heteroaryl; -   R⁴ and R⁵ are independently selected from the group consisting of H,     C₁-C₁₀ alkyl, C₁-C₁₀ alkyl hydroxyl; -   m is 0 or an integer from 1 to 3 and -   n is an integer of from 1 to 4.     Preferably R¹ is OH or O-lower alkyl or N(H)_(p)(lower alkyl)_(q) or     N(H)_(p) (lower alkyl hydroxyl)_(q) wherein p is 0 or 1 and q is 1     or 2. Lower alkyl is defined as a C₁ to C₆ alkyl.     More preferably R¹ is OH or OCH₃.     Preferably the n associated with R² is 1 and R² is lower alkyl.     R³ is preferably selected from the group consisting of phenyl,     furanyl and thienyl.     Finally, preferably the benzylic OH group is oriented as an a OH     group.

Specific compounds of the invention include:

-   7-[[5-Hydroxy-5-(1-propylcyclobutyl)pent-2-enyl]methanesulfonylamino]heptanoic     acid ethyl ester (11). -   7-[[5-Hydroxy-5-(1-propylcyclobutyl)pent-2-enyl]methanesulfonylamino]heptanoic     acid (12).

The compounds of the invention are especially useful in treating ocular hypertension, i.e. lowering elevated intraocular pressure (IOP), and/or glaucoma. These compounds are useful in providing neuroprotection to the eye of a human.

Pharmaceutical compositions including the compounds of this invention may be prepared by combining a therapeutically effective amount of at least one compound according to the present invention, or a pharmaceutically acceptable salt thereof, as an active ingredient, with conventional ophthalmically acceptable pharmaceutical excipients, and by preparation of unit dosage forms suitable for topical ocular use. The therapeutically efficient amount typically is between about 0.0001 and about 5% (w/v), preferably about 0.001 to about 1.0% (w/v) in liquid formulations.

For ophthalmic application, preferably solutions are prepared using a physiological saline solution as a major vehicle. The pH of such ophthalmic solutions should preferably be maintained between 4.5 and 8.0 with an appropriate buffer system, a neutral pH being preferred but not essential. The formulations may also contain conventional, pharmaceutically acceptable preservatives, stabilizers and surfactants.

Preferred preservatives that may be used in the pharmaceutical compositions of the present invention include, but are not limited to, benzalkonium chloride, chlorobutanol, thimerosal, phenylmercuric acetate and phenylmercuric nitrate. A preferred surfactant is, for example, Tween 80. Likewise, various preferred vehicles may be used in the ophthalmic preparations of the present invention. These vehicles include, but are not limited to, polyvinyl alcohol, povidone, hydroxypropyl methyl cellulose, poloxamers, carboxymethyl cellulose, hydroxyethyl cellulose cyclodextrin and purified water.

Tonicity adjustors may be added as needed or convenient. They include, but are not limited to, salts, particularly sodium chloride, potassium chloride, mannitol and glycerin, or any other suitable ophthalmically acceptable tonicity adjustor.

Various buffers and means for adjusting pH may be used so long as the resulting preparation is ophthalmically acceptable. Accordingly, buffers include acetate buffers, citrate buffers, phosphate buffers and borate buffers. Acids or bases may be used to adjust the pH of these formulations as needed.

In a similar vein, an ophthalmically acceptable antioxidant for use in the present invention includes, but is not limited to, sodium metabisulfite, sodium thiosulfate, acetylcysteine, butylated hydroxyanisole and butylated hydroxytoluene.

Other excipient components which may be included in the ophthalmic preparations are chelating agents. The preferred chelating agent is edentate disodium, although other chelating agents may also be used in place of or in conjunction with it.

The ingredients are usually used in the following amounts: Ingredient Amount (% w/v) active ingredient About 0.001-5 preservative  0-0.10 vehicle 0-40 tonicity adjustor 0-10 buffer 0.01-10   pH adjustor q.s. pH 4.5-8.0 antioxidant as needed surfactant as needed purified water as needed to make 100%

The actual dose of the active compounds of the present invention depends on the specific compound, and on the condition to be treated; the selection of the appropriate dose is well within the knowledge of the skilled artisan.

The ophthalmic formulations for use in the method of the present invention are conveniently packaged in forms suitable for metered application, such as in containers equipped with a dropper, to facilitate application to the eye. Containers suitable for dropwise application are usually made of suitable inert, non-toxic plastic material, and generally contain between about 0.5 and about 15 ml solution. One package may contain one or more unit doses.

Especially preservative-free solutions are often formulated in non-resealable containers containing up to about ten, preferably up to about five units doses, where a typical unit dose is from one to about 8 drops, preferably one to about 3 drops. The volume of one drop usually is about 20-35 μl.

The invention is further illustrated by the following examples which are illustrative of a specific mode of practicing the invention and are not intended as limiting the scope of the claims. In the examples, the numbers of the compounds correspond to the numbers in the Figures.

EXAMPLE 1

1-Propylcyclobutanecarboxylic Acid Ethyl Ester (2).

Ethyl cyclobutanecarboxylate 1 (25.0 g, 0.195 mol) was added to a solution of lithium diisopropylamide (97.5 mL of a 2.0M solution in THF, 0.195 mol) in THF (200 mL) at −78° C. After 30 min the reaction solution was warmed to room temperature and transferred via canula to a solution of 1-iodopropane (49.7 g, 0.293 mol) in DMSO (104 mL) while maintaining the temperature between 15-20° C. After stirring for an additional 30 min the precipitated salts were removed by vacuum filtration. The filtrate was concentrated in vacuo, diluted with hexane and washed with 1N HCl, saturated aqueous NaHCO₃ and brine. The organic portion was dried (MgSO₄), filtered and concentrated in vacuo. The residue was purified by vacuum distillation (105-108° C., 20-30 mmHg) to give 16 g (48%) of the ester 2 as a clear, colorless oil.

EXAMPLE 2

1-Propylcyclobutanecarboxaldehyde (3).

Lithium borohydride (4.0 g, 0.186 mol) was added to a solution of the ester 2 (16.0 g, 0.093 mol) in Et₂O (200 mL) at 0° C. The reaction was allowed to warm to room temperature and stirred for 16 h. The reaction was quenched by careful addition of 1N NaOH and extracted with Et₂O. The organic portion was washed with brine, dried (MgSO₄), filtered and concentrated in vacuo to yield the corresponding alcohol as a clear, colorless oil.

Dimethylsulfoxide (28.4 mL, 0.4 mol) was added dropwise to a stirred solution of oxalyl chloride (100 mL of a 2.0M solution in CH₂Cl₂, 0.20 mol) in CH₂Cl₂ (300 mL) at −78° C. After 15 min a solution of the alcohol (prepared above) in CH₂Cl₂ (100 mL) was added and the reaction was stirred for 1 h. Triethylamine (123 mL, 0.88 mol) was added and the reaction was allowed to warm to room temperature. Saturated aqueous NaHCO₃ was added and the organic portion was separated. The organic portion was then washed with brine, dried (MgSO₄), filtered and concentrated in vacuo. FCC (silica gel, 9:1 pentane:CHCl₃) afforded 6.85 g (67%) of the aldehyde 3 as a clear, colorless oil.

EXAMPLE 3

1-(1-Propylcyclobutyl)but-3-yn-1-ol (4).

Propargyl bromide (0.27 mL, 2.4 mmol) was added to a mixture of magnesium (1.1 g, 45 mmol) and mercuric chloride (30 mg, 0.117 mmol) in Et₂O (60 mL). The mixture was warmed to 40° C. until bubbling commenced. The remainder of the propargyl bromide (2.1 mL, 19 mmol) was added in small portions. After −1.5 h the reaction became cloudy white. A solution of the aldehyde 3 (0.8 g, 7 mmol) in Et₂O (4 mL) was added and the reaction was stirred for 16 h. The reaction was then quenched by cautiously adding saturated aqueous NH₄Cl. The resultant mixture was extracted with Et₂O. The organic portion was washed with brine, dried (MgSO₄), filtered and concentrated in vacuo. FCC (silica gel, 1:1 pentane/CH₂Cl₂) gave 1.0 g (94%) of the alcohol 4.

EXAMPLE 4

tert-Butyldimethyl-[1-(1-propylcyclobutyl)but-3-ynyloxy]silane (5).

t-Butyldimethylsilyltrifluoromethanesulfonate (1.8 mL, 7.88 mmol) was added to a solution of triethylamine (2.2 mL, 15.8 mmol) and alcohol 4 (650 mg, 3.94 mmol) in CH₂Cl₂ (5.0 mL) at 0° C. The reaction was stirred for 1 h and then saturated aqueous NaHCO₃ was added. The mixture was extracted with CH₂Cl₂. The organic portion was washed with brine, dried (Na₂SO₄), filtered and concentrated in vacuo. FCC (silica gel, 100% hexane) gave 1.7 g (100%) of the silyl ether 5 as a clear, colorless oil.

EXAMPLE 5

tert-Butyl-[4-iodo-1-(Propylcyclobutyl)but-3-enyloxy]dimethylsilane (6).

Bis(cyclopentadienyl)zirconiumchloride hydride (3.1 g, 12.0 mmol) was added to a solution of alkyne 5 (1.7 g, 3.94 mmol) in CH₂Cl₂ (20 mL) at 23° C. After 0.5 h N-iodosuccinimide (2.6 g, 12.0 mmol) was added. The reaction was stirred for 0.5 h, concentrated in vacuo and the residue was diluted with pentane and washed with saturated aqueous sodium bisulfite. The organic portion was dried (Na₂SO₄), filtered and concentrated in vacuo. Purification of the residue by FCC (silica gel, 100% pentane) gave 1.2 g (71%) of the vinyl iodide 6 as a clear, light yellow oil.

EXAMPLE 6

5-(tert-butyldimethylsilanyloxy)-5-(1-propylcyclobutyl)pent-2-en-1-ol (7).

tert-Butyllithium (1.32 mL of a 1.7M solution in pentane, 2.25 mmol) was added to a solution of the vinyl iodide 6 (460 mg, 1.25 mmol) in THF (2.2 mL) at −78° C. After 0.5 h paraformaldehyde (50 mg, 1.67 mmol) was added. The reaction was warmed to room temperature and stirred for 16 h. The reaction was quenched with saturated aqueous NH₄Cl and extracted with EtOAc. The organic portion was dried (MgSO₄), filtered and concentrated in vacuo. FCC (silica gel, 4:1 hex/EtOAc) yielded 103 mg (33%) of the alcohol 7 as a clear, colorless oil.

EXAMPLE 7

[5-Bromo-1-(1-propylcyclobutyl)pent-3-enyloxy]tert-butyldimethylsilane (8).

Bromine (0.17 mL, 3.22 mmol) was added to a solution of triphenylphosphine (844 mg, 3.22 mmol) and imidazole (219 mg, 3.22 mmol) in CH₂Cl₂ (11.0 mL) at 23° C. After 0.5 h a solution of the alcohol 7 (838 mg, 2.68 mmol) in CH₂Cl₂ (2.7 mL) was added. The reaction was stirred for 1 h, diluted with hexane and then filtered through celite. The filtrate was concentrated in vacuo and purified by FCC (silica gel, 100% hex) to give 870 mg (86%) of the bromide 8 as a clear, light yellow oil.

EXAMPLE 8

7-[[5-((tert-Butyldimethylsilanyloxy)-5-(1-propylcyclobutyl)pent-2-enyl]methanesulfonylamino]heptanoic Acid Ethyl Ester (10).

Sodium bis(trimethylsilyl)amide (1.1 mL of a 1.0M solution in THF, 1.1 mmol) was added to a solution of the sulfonamide 9 (234 mg, 1.07 mmol) in THF (2.2 mL) at 0° C. The reaction was warmed to room temperature and a solution of the bromide 8 (200 mg, 0.533 mmol) in THF (2.0 mL) was added. The reaction was stirred at room temperature for 16 h, quenched with saturated aqueous NH₄Cl and extracted with EtOAc. The organic portion was washed with brine, dried (MgSO₄), filtered and concentrated in vacuo. FCC (silica gel, 6:1 hex/EtOAc) gave 140.7 mg (55%) of the silyl ether 10 as a light yellow viscous oil.

EXAMPLE 9

7-[[5-Hydroxy-5-(1-propylcyclobutyl)pent-2-enyl]methanesulfonylamino]heptanoic Acid Ethyl Ester (11).

Tetrabutylammonium fluoride (0.58 mL of a 1.0M solution in THF, 0.58 mmol) was added to a solution of the silylether 10 (140.7 mg, 0.29 mmol) in THF (4.5 mL) at 23° C. The reaction was stirred for 16 h, diluted with EtOAc and washed with water. The organic portion was washed with brine, dried (MgSO₄), filtered and concentrated in vacuo. FCC (silica gel, 1:1 hex/EtOAc) afforded 97.8 mg (91%) of the alcohol 11 as a light yellow, viscous oil.

EXAMPLE 10

7-[[5-Hydroxy-5-(1-propylcyclobutyl)pent-2-enyl]methanesulfonylamino]heptanoic Acid (12).

Lithium hydroxide (0.50 mL of a 0.5N solution in H₂O, 0.122 mmol) was added to a solution of the ester 11 (45 mg, 0.122 mmol) in THF (1.0 mL) at 23° C. The reaction mixture was stirred for 16 h, acidified with 1 N HCl and extracted with EtOAc. The organic portion was washed with brine (2×), dried (MgSO₄), filtered and concentrated in vacuo. FCC (silica gel, 100% EtOAc) gave 36.2 mg (72%) of the free acid 12 as a light yellow, viscous oil.

In an in-vitro assay for binding to and activity at prostaglandin receptors, the compound of Example 10 was shown to be selective at the EP2 and EP4 receptors as compared to the FP, EP1, TP, IP and DP receptors. TABLE Compound cAMP bhEP₂ fhEP₂ bhEP₄ fhEP₄

5560 248 50K 15K 12

While particular embodiments of the invention have been described it will be understood of course that the invention is not limited thereto since many obvious modifications can be made and it is intended to include within this invention any such modifications as will fall within the scope of the appended claims. 

1. A compound represented by the formula:

wherein R¹ is selected from the group consisting of C₁-C₁₀ alkoxy, OH and NR⁴R⁵; R² is selected from the group consisting of C₁-C₁₀ alkyl and (CH₂)_(n)OH; R³ is selected from the group consisting of C₁-C₁₀ alkyl, heteroaryl, e.g. thienyl, furanyl and pyridyl, phenyl, mono, -di-, tri-substituted phenyl and heteroaryl; R⁴ and R⁵ are independently selected from the group consisting of H, C₁-C₁₀ alkyl, C₁-C₁₀ alkyl hydroxyl; m is 0 or an integer from 1 to 3 and n is an integer of from 1 to
 4. 2. The compound of claim 1 wherein R³ is selected from the group consisting of thienyl, furanyl and pyridyl.
 3. The compound of claim 1 wherein R³ is selected from the group consisting of C₁-C₁₀ alkyl.
 4. The compound of claim 1 wherein R¹ is OH or O-lower alkyl, wherein said lower alkyl is a C₁-C₆ alkyl.
 5. The compound of claim 1 wherein R¹ is selected from the group consisting of N(H)_(p)(lower alkyl)_(q) or N(H)_(p) (lower alkylhydroxyl)_(q) wherein said lower alkyl is a C₁-C₆ alkyl and wherein p is 0 or 1 and q is 1 or
 2. 6. The compound of claim 1 wherein R² is a C₁-C₁₀ alkyl.
 7. The compound of claim 1 that 7-[[5-Hydroxy-5-(1-propylcyclobutyl)pent-2-enyl]methanesulfonylamino]heptanoic acid ethyl ester.
 8. The compound of claim 1 that is 7-[[5-Hydroxy-5-(1-propylcyclobutyl)pent-2-enyl]methanesulfonylamino]heptanoic acid.
 9. A method for treating ocular hypertension or glaucoma which comprises administering to a mammal having ocular hypertension a therapeutically effective amount of a compound of the formula

wherein R¹ is selected from the group consisting of C₁-C₁₀ alkoxy, OH and NR⁴R⁵; R² is selected from the group consisting of C₁-C₁₀ alkyl and (CH₂)_(n)OH; R³ is selected from the group consisting of C₁-C₁₀ alkyl, heteroaryl, phenyl, mono, -di-, tri-substituted phenyl and heteroaryl; R⁴ and R⁵ are independently selected from the group consisting of H, C₁-C₁₀ alkyl, C₁-C₁₀ alkyl hydroxyl and n is 0 or
 1. 10. The method of claim 1 wherein R³ is selected from the group consisting of thienyl, furanyl and pyridyl.
 11. The method of claim 1 wherein R³ is selected from the group consisting of C₁-C₁₀ alkyl.
 12. The method of claim 1 wherein R¹ is OH or O-lower alkyl, wherein said lower alkyl is a C₁-C₆ alkyl.
 13. The method of claim 1 wherein R¹ is selected from the group consisting of N(H)_(p)(lower alkyl)_(q) or N(H)_(p) (lower alkylhydroxyl)_(q) wherein said lower alkyl is a C₁-C₆ alkyl.
 14. The method of claim 1 wherein R² is a C₁-C₆ lower alkyl and the n associated with R₂ is
 1. 15. The method of claim 1 wherein said compound is 7-[[5-Hydroxy-5-(1-propylcyclobutyl)pent-2-enyl]methanesulfonylamino]heptanoic acid ethyl ester).
 16. The method of claim 1 wherein said compound is 7-[[5-Hydroxy-5-(1-propylcyclobutyl)pent-2-enyl]methanesulfonylamino]heptanoic acid.
 17. An ophthalmic solution comprising a therapeutically-effective amount of the compound of claim 1 in ophthalmically-acceptable vehicle.
 18. The solution of claim 17 wherein said vehicle is saline.
 19. The solution of claim 17 wherein said compound comprises from 0.001-5% w/v of said solution.
 20. A method of providing neuroprotection to the eye of a mammal which comprises administering to the eye of said mammal a compound represented by the formula:

wherein R¹ is selected from the group consisting of C₁-C₁₀ alkoxy, OH and NR⁴R⁵; R² is selected from the group consisting of C₁-C₁₀ alkyl and (CH₂)_(n)OH; R³ is selected from the group consisting of C₁-C₁₀ alkyl, heteroaryl, e.g. thienyl, furanyl and pyridyl, phenyl, mono, -di-, tri-substituted phenyl and heteroaryl; R⁴ and R⁵ are independently selected from the group consisting of H, C₁-C₁₀ alkyl, C₁-C₁₀ alkyl hydroxyl; m is 0 or an integer from 1 to 3 and n is an integer of from 1 to
 4. 